SX nickel-based superalloys reinforced with γ′ cannot be subjected to build-up welding with fillers of the same type in overlapping welding tracks in one or more layers either by means of conventional welding processes or by high-energy processes (laser, electron beam). The problem is that a microstructure with misorientation already forms in the case of an individual welding track in the marginal region close to the surface. For the subsequent overlapping track, this means that the solidification front in this region has no available SX nucleus, and the region with misorientation (no SX microstructure) expands further in the overlapping region. Cracks are formed in this region.
For SX nickel-based superalloys reinforced with γ′, the welding processes used to date are not able to homogeneously build up a weld metal by overlapping in one or more layers with an identical SX microstructure. In the case of a single track on an SX substrate, the local solidification conditions vary in such a manner that, depending on the position, dendritic growth is initiated proceeding from the primary roots or the secondary arms. In this case, of the various possible dendrite growth directions, the direction which prevails is the direction with the most favorable growth conditions, i.e. the direction with the smallest angle of inclination with respect to the temperature gradient. The cause of the formation of misorientations in the SX microstructure during the powder build-up welding of SX nickel-based superalloys reinforced with γ′ has not yet been completely clarified. It is suspected that, when the dendrites meet one another from various growth directions, secondary arms may break away and serve as nuclei for the formation of a misoriented microstructure. In addition, powder particles which have not completely melted in the melt may serve as nuclei for the formation of a misoriented microstructure in the marginal region close to the surface. To solve this problem, a procedure which involves realizing growth conditions which favor only one growth direction for the dendrites is therefore proposed for the powder build-up welding of SX nickel-based superalloys reinforced with γ′. In addition, the procedure ensures that the powder particles are melted completely in the melt.